The present invention relates to pumpable, freeflowing aqueous coal dispersions which contain a special non-ionic dispersant and may or may not contain methanol, and to the use of a special non-ionic dispersant in coal/water dispersions.
Aqueous coal dispersions have recently become more important, particularly beccause they can be transported advantageously, for example in pipelines.
U.S. Pat. No. 4,358,293 discloses aqueous coal dispersions which contain relatively high molecular weight polyalkylene oxides as non-ionic surface-active dispersants. The compounds described include polyalkylene oxides of alkylphenols, such as nonylphenoxypolyethylene oxide containing more than 100 ethylene oxide units.
It has been found that the various surfactants are not particularly suitable for use in all cases, ie. they cannot be used for all types of coal. Moreover, some of the dispersants used to date are difficult to handle since they may dissolve very slowly in water and in some cases concentrated aqueous solutions cannot be prepared.
German Laid-Open Applications DOS No. 2,745,449 and DOS No. 2,751,519 disclose that polyalkylene oxide derivatives of bisphenol A derivatives, in particular in the sulfated form, are used as dispersants for disperse dyes and for optical brighteners which are sparingly soluble or insoluble in water. The stated dispersants are used in an amount of from 10 to 200% by weight, based on the amount of dispersed substances. Such an amount is completely unacceptable, for example, for aqueous coal dispersions.